Drawing synthetic thermoplastic yarn

ABSTRACT

FILAMENTARY YARN COMPOSED OF THERMOPLASTIC SYNTHETIC, ORGANIC POLYMERS IS UNIFORMLY DRAWN AT HIGH SPEED BY DIRECTING A STREAM OF HEATED LIQUID INTO THE PATH OF THE YARN TO HEAT THE LATTER TO DRAWING TEMPERATURE AT LESS THAN DRAWING TENSION AND IMMEDIATELY THEREAFTER DRAWING THE YARN BY PASSING IT OVER ONE OR MORE SNUBBING PINS ARRANGED CLOSE TO BUT OUT OF CONTACT WITH THE LIQUID STREAM.

Jan. 19, 1971 w, R wE- 3,557,273

DRAWING SYNTHETIC THERMOPLASTIC YARN Original Filed June 25; 1965 United States Patent US. Cl. 264--210 6 Claims ABSTRACT OF THE DISCLOSURE 'Filamentary yarn composed of thermoplastic synthetic, organic polymers is uniformly drawn at high speed by directing a stream of heated liquid into the path of the yarn to heat the latter to drawing temperature at less than drawing tension and immediately thereafter drawing the yarn by passing it over one or more snubbing pins arranged close to but out of contact with the liquid stream.

This application is a streamlined continuation of application Ser. No. 467,076, filed June 25, 1965 and now abandoned.

This invention relates to apparatus for uniformly drawing filamentary yarns composed of thermoplastic, synthetic, organic polymers and to a process for drawing such yarns.

Apparatus and processes for orienting synthetic thermoplastic yarns which have been proposed are many and varied, some being specifically designed for use with yarns of particular polymers and others being of more general utility. Apparatus heretofore described has included drawing by means of heated snubbing pins, heated feed rolls, partly or completely liquid-immersed snubbing pins and liquid or vapour baths. Many of these forms of apparatus possess limitations, as for example limited drawing speed or not entirely uniform products.

We have now found that uniform drawing at high speeds may be effected by means of a combination of a stream of hot liquid and one or more snubbing pins.

According to the present invention we provide apparatus for drawing filamentary yarns composed of thermoplastic synthetic onganic polymers comprising means for supplying yarn to a drawing device, means for withdrawing yarn from the drawing device at a higher rate than the supply rate and means for collecting the drawn yarn, wherein the drawing device comprises a supply of temperature-controlled liquid and means for directing a stream of the liquid into the path of the incoming yarn just prior to passing the yarn over snubbing means, whereby the yarn is raised to the desired drawing temperature, said snubbing means being out of direct contact with the liquid stream and so arranged as to cause in operation a sudden change in direction of the yarn whereby liquid entrained in the yarn is thrown off.

Further according to the present invention we also provide a process for the high speed uniform drawing of filamentary yarns composed of thermoplastic synthetic organic polymers, wherein yarn is heated to a desired drawing temperature by a stream of liquid directed into the path of the yarn just prior to passage of the yarn over snubbing means arranged close to but not in direct contact with said stream.

Any liquid which does not attack the yarn to be drawn may be used to heat the yarn prior to drawing on the snubbing means and water is generally the most useful liquid. The liquid may be supplied from a reservoir of liquid held at the required temperature to which the liquid after passing through the drawing device is recirculated.

Alternatively the liquid may be continuously circulated "ice through the drawing device at the desired temperature being either run to waste after passage therethrough or recirculated with addition of heat to maintain the temperature substantially constant. Lubricating or other substances may be applied to the yarn simply by dissolving or dispersing such materials in the heating liquid.

The means for directing the liquid onto the yarn may be, for example, a jet or flume by means of which the direction of the issuing liquid can be controlled. The direction of the issuing liquid may be counter or co-current in relation to the direction' of the yarn travel.

Snubbing means may conveniently have the form of one or more metal or ceramic pins, preferably of cylindrical shpae, though other shapes may be used, arranged close to, but out of direct contact with the stream of heating liquid. In this way substantially no loss of heat from the yarn occurs before it reaches the snubbing means whereon the tension in the yarn is raised until drawing ensues. The snubbing pin or pins is or are arranged so as to cause in operation the sudden change or changes of direction of travel of the yarn to throw off adhering liquid but the arrangement is such that the temperature of the yarn is not allowed to fall very far below the desired drawing temperature until drawing is substantially complete.

The main function of the snubbing means in this invention is to raise the tension in the yarn, which already has been brought to the desired drawing temperature by means of the liquid jet, to that at which drawing ensues. The snubbing means may be heated but it is not necessary to do so for adjustment of the temperature of the liquid jet and its position relative to the snubbing means will ensure that the yarn passes over the latter at the desired drawing tempearture.

The function of the liquid jet is to raise the yarn to the desired drawing temmrature, which temperature is chosen to suit the particular synthetic polymer yarn to be drawn. The tension in the yarn passing through the liquid jet is kept lower than that at which drawing commences under the applied temperature conditions. Thus operating conditions are arranged such that substantially no drawing occurs until the yarn reaches the snubbing means. Control of the operating conditions in this way results in the production of highly uniformly drawn yarn and such control is facilitated by the drawing device of the present invention, wherein heating of the yarn takes place substantially in the absence of any tension raising influence.

It is only necessary to limit the length of the yarn immersed in the liquid jet so that the yarn tension is not raised to the drawing tension at the temperature used by the liquid drag on the yarn travelling at high speed.

Uniformity of the drawn yarn may be assessed in various ways and for polyethylene terephthalate yarn we have used dyefleck or stripiness tests for this purpose. In the dyefieck test a uniform layer of drawn yarn is wound onto a parallel tube by means of a lathe. The bobbin and yarn are immersed in a cold acetone solution of the solvent dyestutf Waxoline Red OS (Colour Index No. 26105), a dyestutf which does not dye drawn yarn but dyes undrawn yarn red. After rinsing in acetone the tube is examined and the dyeflecks, that is lengths of un drawn fibre, are counted. The result is expressed as the number of dyeflecks per 24,000 feet of filament.

For assessing the stripiness of drawn yarn an S-end sateen fabric is woven and dyed with an appropriate dye stuff for the particular synthetic polymer yarn being assessed, as for example Dispersol fast scarlet B (Colour Index No. 11110) for polyethylene terephthalate using 2% of the dyestuff based on the weight of the fabric. The dyed fabric is examined visually under natural and ultraviolet light for stripiness, i.e. uneven dyeing of lengths of warp or weft which are evident in the fabric as warp or weft stripes.

The liquid directing means and the snubbing means are conveniently arranged in one unit. A preferred embodiment of the apparatus of the invention comprising such a unit is illustrated by way of example, in the accompanying drawing wherein:

FIG. 1 diagrammatically shows in cross section a side elevation of a drawing device, together with representations of yarn supplying, withdrawing and collecting means.

FIG. 2. diagrammatically shows a sectional plan view of a drawing device.

In the apparatus of FIGS. 1 and 2, liquid at the required temperature is supplied from a source (not shown) through an inlet 1, to directing means, 2, which has the form of a truncated flume, 4, mounted within a container, 3. The liquid flows from the narrower end of the fiume across the path of entering yarn, 5, just before the yarn is passed over the first of a series of three snubbing pins, 6, Whereon the tension is raised and drawing occurs. The snubbing pins are mounted on a carrier, 7, which is attached to a cover, 8, of the container, 3, the whole being demountable to facilitate stringing-up of the yarn. The used liquid is carried away by way of an outlet, 9, to waste or to a temperature controlled reservoir (not shown).

Spun yarn is supplied to the drawing device from a package, 10, by a feed/roll idler roll combination, 11, optionally by way of a tension control device, 12. Drawn yarn leaves the drawing device by a draw roll/idler roll combination, 13, and is collected on a package, 14.

In an apparatus according to the invention the amount of entrained liquid, if any, in the drawn yarn leaving the drawing device is dependent upon the number of snubbing pins or guides within the device and the sharpness of changes of direction incurred at each. It is not necessary or indeed possible in the practice of the invention to ensure that all entrained liquid is removed from the drawn yarn in the drawing device. It is often convenient to remove a substantial proportion of entrained liquid in the drawing device and then to remove the remainder by, for example, heating the draw roll causing evaporation of the liquid thereon. Heating the draw roll serves a secondary function, that of heat treating the drawn yarn at controlled tension to modify the physical properties, in particular shrinkage, of the yarn.

By means of this invention uniformly drawn yarns may be obtained at high speeds. Heating of the yarn to be drawn by liquid means, as in the invention, enables higher speeds of drawing to be attained because of the improved uniformity and rate of heating-up of the yarn and because of the substantial absence of any snubbing surfaces in contact with the yarn at this stage. Likewise accurate temperature control is facilitated by use of a large body of liquid in a temperature-controlled reservoir. Surprisingly we have found that filamentary yarns composed of polyethylene terephthalate, which are usually drawn at elevated temperatures between about 70 C. and 100 C. i.e. a temperature at or above the second order transition temperatures may be uniformly drawn by means of a device according to this invention at temperatures approaching room temperature i.e. a temperature well below the second order transition temperature, without any apparent deterioration in uniformity. If instead such polyethylene terephthalate yarns are drawn by means of an unheated snubbing surface alone, very uneven yarn is produced and only very low speeds of drawing are possible without breakdown of the yarn.

By means of the present invention we have drawn polyethylene terephthalate yarns at speeds up to 7,200 feet per minute, which was the limit of the available winding units, without the appearance of non-uniformities as assessed by the dyefleck test. By comparison using a known drawing process wherein yarn is drawn between a heated feed roll (90 C.) and a cold draw roll with a heated plate (140160 C.) intermediate these rolls it was not possible to exceed a draw speed of about 5,000 feet per 4 minute without incurring the appearance of dyeflecks in the yarn.

Yarn composed of polyethylene terephthalate, 24 filaments of 5 denier per filament, drawn with a draw ratio of 3.22:1 in the apparatus of FIGS. 1 and 2, using Water at '80" C. as the heating liquid and a draw speed of 3,000 ft./min. gave a 40 denier drawn yarn which was highly uniform in respect of denier differences along its length.

A particular advantage of the high drawing speed at tainable by the device of this invention is that the drawing step may be combined with the melt-spinning process in one stage and not as the usual two-stage process on separate apparatus, wherein drawing follows melt-spinning as a separate process, necessitated by the lower (than the melt-spinning winding speed) drawing speed required with many other forms of drawing apparatus.

Any filamentary yarn which is composed of a thermoplastic cold-drawable, synthetic polymer may be drawn by means of the device of this invention. For example we have drawn polyethylene terephthalate, nylon 66 and polypropylene yarns by means of the device.

The following examples illustrate the invention and the manner in which it may be performed.

EXAMPLES 1-3 Filamentary yarn composed of 24 filaments of polyethylene terephthalate having total denier of 160 and a mean birefringence of 8.3 10 is drawn at a draw-ratio of 3.22:1 using an apparatus similar to that of FIGS. 1 and 2 but having only a single ceramic pin of inch diameter as the snubbing means. The heating liquid is water, containing 1% by weight of a lubricant/antistat dispersed therein, maintained at C. directed co-current onto the yarn and giving an immersed yarn length of 2 inches. The angle of contact of the yarn with the snubbing pin is 90 C. Yarn drawn at different speeds using a cool (30 C., Example 1) or heated (160 C., Examples 2-3) draw roll shown no dyeflecks and has the following properties:

Draw

roll Tenae- Shrinkage in Draw temperity, Extension boiling speed, ature grarn/ at break, water, ft./min. C. denier percent percent;

Fabric woven from the yarn produced in Examples 2 and 3 shows no stripiness.

It is noteworthy that when the Example 2 is repeated using 4 /2 inches yarn immersed length and a draw speed of 3,500 feet per minute uneven drawing, with the production of dyeflecks, resulted due to some drawing taking place in the liquid stream by reason of the increased water drag.

EXAMPLE 4 In this example the polyester yarn as used in Examples 1-3 is very satisfactorily drawn in the same apparatus at a draw ratio of 3.22:1 to produce dyefleok-free yarn using a reduced liquid temperature of 56 C., a draw speed of 2,000 feet per minute and a cold (20 C.) draw roll. The drawn yarn has the following properties:

Tenacity, g./den. 4.1 Extension at break, percent 28.1 Boiling water shrinkage, percent 32.1

EXAMPLE 5 Yarn as used in the preceding examples is drawn (draw ratio 3.27:1) in the same apparatus using the maximum draw speed of 7,200 ft./min. available from the winding unit. A liquid temperature of 80 C., an immersed length of 1% inches and a hot C.) draw roll are used and yarn, completely free from dyefiecks, having the following properties is produced:

Tenacity, g./den. 4.9 Extension at break, percent 19.5 Boiling water shirinkage, percent 4.7

EXAMPLE 6 Nylon 66 yarn of 803 denier and 34 filaments (mean birefringence 5.2 10* is drawn in the apparatus of the preceding examples at 5,000 ft./1nin. using a draw ratio of 3.27:1 and a cold draw roll. The yarn draws satisfactorily in the presence of a stream of water (temperature 76 C.) to produce uniform yarn of similar properties. In the absence of the water stream the yarn shows marked non uniformity of drawing when knitted into a fabric and dyed with Durazol Blue 2R (Colour Index No. 34140).

EXAMPLE 7 The apparatus of FIGS. 1 and 2 is used with an arrangement of five ceramic pins of inch diameter to draw the same polyester yarn used in Example 4 at a draw speed of 2,000 ft./min. and a draw ratio of 3.22:1. A liquid temperature of 82 C. is used with a hot draw roll at 7 140 C. The five pins are arranged one above the other /2 inch apart in staggered fashion inch stagger between adjacent pins) and the yarn takes a zig-zag path over the pins with contact angles on the first and fifth pins of 130 and 45 respectively, and on the three intermediate pins of 90 C.

The yarn produced has substantially the same properties as yarn produced in Example 4 and is free from dyeflecks.

I claim:

1. In a one-stage melt-spinning and drawing system the process for the high speed uniform drawing of filamentary yarns composed of thermoplastic synthetic organic polymers selected from the group consisting of polyethylene terephthalate, nylon 66 and polypropylene polymers comprising heating the yarn without prior heating substantially in the absence of any tension-raising influence to a desired drawing temperature by a stream of heated liquid directed into the path of the yarn while maintaining the tension in the yarn passing through the liquid stream below the tension at which drawing occurs so that the yarn remains substantially undrawn in its passage through the liquid stream and immediately thereafter drawing the heated yarn by passing it over snubbing means arranged close to but not in direct contact with said stream.

2. A process according to claim 1 wherein the yarn in its passage over the snubbing means is caused to change direction sharply thereby throwing 01f liquid entrained in it.

3. A process according to claim 1 wherein the liquid is water.

4. A process according to claim 1 wherein the liquid contains a lubricating substance.

5. A process according to claim 1 wherein the stream of liquid is countercurrent to the direction of travel of the yarn.

6. A process according to claim 1 wherein the stream of liquid is co-current with the direction of travel of the yarn.

References Cited UNITED STATES PATENTS 2,942,325 6/1960 Spellman,]r 264290 3,303,169 2/1967 Pitzl 264-2101 3,091,805 6/1963 Dusenbury 264290T FOREIGN PATENTS 229,852 8/1960 Australia 264288 597,765 5/1960 Canada 264290 JU-LIUS FROME, Primary Examiner H. MINTZ, Assistant Examiner US. Cl. X.R. 181; 264-290 

